Console and Auxiliary Port Considerations

About Console and Auxiliary Ports

The router includes USB, asynchronous serial and auxiliary ports. The console and auxiliary ports provide access to the router either locally using a console terminal connected to the console port, or remotely, using a modem connected to the auxiliary port. This section provides important cabling information to consider before connecting the router to a console terminal or modem.

The main difference between the console and auxiliary ports is that the auxiliary port supports flow control, whereas the console port does not. Flow control paces the transmission of data between a sending device and a receiving device. Flow control ensures that the receiving device can absorb the data sent to it before the sending device sends more. When the buffers on the receiving device are full, a message is sent to the sending device to suspend transmission until the data in the buffers has been processed. Because the auxiliary port supports flow control, it is ideally suited for use with the high-speed transmissions of a modem. Console terminals send data at slower speeds than modems; therefore, the console port is ideally suited for use with console terminals.

Console Port Connections

The router has an EIA/TIA-232 asynchronous serial console port (RJ-45) and at least one USB Type-A 2.0 compliant ports. See Table 1-1 for a list of ports.

USB Serial Console

The USB serial console port connects directly to the USB connector of a PC using a USB Type A to 5-pin mini Type-B cable. The USB Console supports full speed (12Mb/s) operation. The console port does not support hardware flow control.

For operation with Microsoft Windows, the Cisco Windows USB Console Driver must be installed on any PC connected to the Console port. If it is not installed, prompts guide you through a simple installation process.

The Cisco Windows USB Console Driver allows plugging and unplugging the USB cable from the console port without affecting Windows HyperTerminal operations. No special drivers are needed for Mac OS X or Linux.

Only one console port can be active at a time. When a cable is plugged into the USB console port the RJ 45 port becomes inactive. Conversely, when the USB cable is removed from the USB port the RJ 45 port becomes active.

Note 4-pin mini Type-B connectors are easily confused with 5-pin mini Type-B connectors. They are not compatible Only the 5-pin mini Type-B can be used.

USB Console OS Compatibility

Windows 2000, Windows XP 32- and 64-bit, Windows Vista 32- and 64-bit

Mac OS X version 10.5.4

Redhat / Fedora Core 10 with kernel 2.6.27.5-117

Ubuntu 8.10 with kernel 2.6.27-11

Debian 5.0 with kernel 2.6

Suse 11.1 with kernel 2.6.27.7-9

Auxiliary Port Connections

The router has an EIA/TIA-232 asynchronous serial auxiliary port (RJ-45) that supports flow control. Depending on the cable and the adapter used, this port will appear as a DTE or DCE device at the end of the cable.

For connection to a modem use an RJ-45-to-DB-9 cable and a DB-9-to-DB-25 adapter.

About Serial Connections

Before you connect a device to a serial port, you need to know the following:

Type of device—data terminal equipment (DTE) or data communications equipment (DCE)—that you are connecting to the synchronous serial interface

Type of connector—male or female—that is required for connecting to the device

Signaling standard that is required by the device

Configuring Serial Connections

The serial ports on the serial WICs use DB-60 connectors. Serial ports can be configured as DTEs or DCEs, depending on the serial cable used.

Serial DTE or DCE Devices

A device that communicates over a synchronous serial interface is either a DTE or DCE device. A DCE device provides a clock signal that paces the communications between the device and the router. A DTE device does not provide a clock signal. DTE devices usually connect to DCE devices. The documentation for the device should indicate whether it is a DTE or DCE device. (Some devices have a jumper that allows you to select either DTE mode or DCE mode.) Table 3-1 lists typical DTE and DCE devices.

1.If pins protrude from the base of the connector, the connector is male.

2.If the connector has holes to accept pins, the connector is female.

Signaling Standards Supported

The synchronous serial ports available for the router support the following signaling standards: EIA/TIA-232, EIA/TIA-449, V.35, X.21, and EIA-530. You can order a Cisco DB-60 shielded serial transition cable that has the appropriate connector for the standard you specify. The documentation for the device that you want to connect should indicate the standard used for that device. The router end of the shielded serial transition cable has a DB-60 connector, which connects to the DB-60 port on a serial WIC. The other end of the serial transition cable is available with a connector appropriate for the standard that you specify.

The synchronous serial port can be configured as DTE or DCE, depending on the attached cable (except EIA-530, which is DTE only). To order a shielded cable, contact customer service. See the “$paratext>” section.

Note All serial ports configured as DTE require external clocking from a channel service unit/data service unit (CSU/DSU) or other DCE device.

Transmission Speeds and Distance Limitations

Serial signals can travel a limited distance at any given bit rate; generally, the slower the data rate, the greater the distance. All serial signals are subject to distance limits, beyond which a signal is significantly degraded or is completely lost.

Table 3-2 lists the recommended maximum speeds and distances for each serial interface type; however, you might get good results at speeds and distances greater than those listed, if you understand the electrical problems that might arise and can compensate for them. For instance, the recommended maximum rate for V.35 is 2 Mbps, but 4 Mbps is commonly used.

Table 3-2 Serial Signal Transmission Speeds and Distances

Distance for EIA/TIA-232

Distance for EIA/TIA-449, X.21, V.35, and EIA-530

Distance for USB

Rate (bps)

Feet

Meters

Feet

Meters

Feet

Meters

2400

200

60

4100

1250

16.4

5

4800

100

30

2050

625

16.4

5

9600

50

15

1025

312

16.4

5

19200

25

7.6

513

156

16.4

5

38400

12

3.7

256

78

16.4

5

56000

8.6

2.6

102

31

16.4

5

1544000 (T1)

—

—

50

15

16.4

5

Balanced drivers allow EIA/TIA-449 signals to travel greater distances than EIA/TIA-232 signals. Typically, EIA/TIA-449 and EIA-530 can support a 2-Mbps rate, and V.35 can support a 4-Mbps rate.

Asynchronous/Synchronous Serial Module Baud Rates

The following baud-rate limitations apply to the slow-speed serial interfaces in the asynchronous/synchronous serial modules:

Asynchronous interface—Maximum baud rate is 115.2 kbps.

Synchronous interface—Maximum baud rate is 128 kbps, full-duplex.

ISDN BRI Connections

The BRI WICs provide Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) connections. BRI WICs are available with either an S/T interface that requires an external Network Termination 1 (NT1), or a U interface that has a built-in NT1. You can install the BRI WICs in any available WIC slots in the chassis.

Warning The ISDN connection is regarded as a source of voltage that should be inaccessible to user contact. Do not attempt to tamper with or open any public telephone operator (PTO)-provided equipment or connection hardware. Any hardwired connection (other than by a nonremovable, connect-one-time-only plug) must be made only by PTO staff or suitably trained engineers. Statement 23

Warning Hazardous network voltages are present in WAN ports regardless of whether power to the unit is OFF or ON. To avoid electric shock, use caution when working near WAN ports. When detaching cables, detach the end away from the unit first. Statement 1026